The present invention concerns an RFI (radio frequency interference) shield for and IR (infra-red) transducer.
Since input circuits including an IR transducer for converting IR radiation to corresponding electrical signals operate at low signal levels, they are susceptible to RFI caused by electromagnetic radiation in undesired frequency ranges. While the circuits may be to some degree designed to reject electrical signal due to RFI, such circuits tend to be too expensive for use in consumer products. As an alternate to RFI rejection circuitry some form of grounded metal RFI shield may be employed.
The shielding effects of an RFI shield for an IR input circuit is limited due to the aperture(s) necessary for the reception of IR radiation. To partially cure this problem, a metal screen or mesh may be placed over the aperture(s) of a RFI shield. The metal screen permits IR radiation to reach the IR transducer and tends to, at least partially, provide some RFI shielding in the area of the aperture. Unfortunately, the two piece construction of metal shield and screen is expensive. Moreover, the two piece construction is subject to the degradation of the electrical contact between the screen and metal shield which tends to reduce its RFI shielding effectiveness.